Has there been any inexpensive item that enhanced your system's sound?


For me it was an inexpensive power cord that was laying around for years, a Pangea AC9.  I have it connected to my Yamaha A S2000.  I've tried the stock cord on the Yamaha and then some of my other cords, (Wireworld, VH Flavor 4, Acronlink/Oyaide custom cord and a MAC). I've had lots of amps and integrated amps over the years, and this is the first time the Pangea contributed to making better sound. It surprised me because I had tossed it aside and forgot about it.  Power cord performance is such a crap-shoot and dependent on so many other variables in the audio chain.  Any inexpensive item you've come across that enhanced your system's sound? 
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$4 foam bass traps and a $17 bottle of Stranahan’s Colorado single malt.Anyone else using Glencairn whisky glasses? They enhance the depth and widen the stage of the olfactory experience.So we have sound, sight, smell, taste and some tactile impact.That’s as much as I care to imagine. You’re on your own.
Adding this WAudio W-3900 power conditioner to the list. It cost very little by audiophile standards, but it really does a fantastic job in my setup with a Maestro Outlet> W-3900 (using stock power cord as a baseline)>Silver Audio Wattmaster PC>PS Audio Nuwave DAC. Available at Amazon (Prime).